September 5, 2017 at 3:32 p.m.
University of Wisconsin-Madison researchers delved into factors linked to milk production, from cows on pasture on organic farms. The most important factor - for at least one part of the grazing season - was the amount of time a farmer had been using managed, rotational grazing.
"For September, the first thing that popped out was having over 20 years of experience with grazing," said Chelsea Hoban-Zeglar, who assisted with the research. She and UW-Madison weed scientist Mark Renz talked about the study during a field day Aug. 12 at the organic dairy farm of Don and Samantha Frei near Argyle, Wis.
The paddocks were examined twice in a year - in June and September. Twenty farms in northern and southern Wisconsin, plus one in northeast Iowa, participated in the study.
The study lasted two years, with 10 farms participating each year, said Renz. Each farmer was asked to choose two paddocks to be investigated for factors like productivity, the kinds of plants growing and an estimate of forage quality.
Along with examining the pastures, researchers tested for soil fertility in October. Over the winter, the farmers were asked questions about the paddocks' management.
Researchers entered all the information into a computer program. The results show that having 20 or more years of experience mattered greatly - especially in September. The findings surprised some of the approximately 80 people at the field day.
Zeglar said the experience factor indicates that a lot of other variables are at play when it comes to optimally managing pastures. She said, in addition, that experience counted for more than twice as much as the second-most important factor.
1,200 pounds of dry matter
For the entire year, two factors were deemed the most important.
"On average, we found that if you could produce a little over a thousand pounds of forage - 1,200 pounds of forage per acre - that was really the cut-off between getting more milk and less milk from the pastures," Renz said.
At least 1,200 pounds of feed per acre needed to be available to the cows during each grazing event or every time the animals were turned into the paddock.
But, it wasn't just the amount of feed available that mattered. It also had to be of the right quality.
"NDF (neutral detergent fiber) below 42 percent appeared to be a really critical factor," said Renz.
For June, the study found that the most important factor for high milk production was the amount of improved legumes in the pasture. Improved plants are those specifically seeded by someone - not those that simply appear. These legumes include alfalfa, red clover and white clover that was not Dutch white. The presence of improved legumes was deemed four times more important than the next factor.
The next-most important June factor was the pasture's residual height - its height at the end of the grazing season. The most milk was produced during the year following grazed pastures where the plants were more than three inches tall going into winter. Zeglar said taller plants get going better in the spring.
The third-most important June factor was having less than 50 percent of a pasture growing unimproved grasses, such as Kentucky bluegrass and quackgrass. Less grass cover, said Zeglar, means there's more room for legumes.
The fourth and fifth most important factors in June were having enough zinc and magnesium in the soil. But, having enough legumes was eight times as important.
The second-most important factor during September - behind having at least 20 years of experience - turned out to be flatter paddocks, with slopes of less than eight percent, Zeglar said. The next factor was less Kentucky bluegrass in the pastures in September - under 65 percent.
Behind experience and slope was leaving more residue in the pastures at the end of the grazing season. The best-performing pastures had plants at an average height above four inches.
While the research focused on the paddocks mainly in June and September, it also delved into some of the factors that seemed to make for better grazing -and higher milk production - during September and among the more-experienced graziers.
Graziers with at least two decades of experience under their belts had more orchardgrass in their pastures during September - about 50 percent, compared to 20 percent for those with less experience.
Veteran graziers also had shorter pastures when the cows were turned into them for the first time in the spring. These graziers also averaged a 32 percent cover of unimproved grasses in their paddocks, versus 55 percent for the less-experienced people.
Having more improved legumes was found to be the next-most important factor. Then came leaving a taller residue after reach round of grazing.
"It might have been only half an inch more," said Zeglar. "But, it added up throughout the season by leaving the plants more leaf area to collect energy and produce more."[[In-content Ad]]
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